As we shop in the supermarket, my wife whispers, "Is she pregnant?" "No, that's probably just her spare tire," I reply. Supermarket checkout aisles show magazines promising to help you "Lose 20 pounds (9 kg) in 10 days!"

My wife and I often see an obese homeless woman in a wheelchair outside one store. We talked to her once. It turns out that she was in the wheelchair because she was so huge. She asked us if we knew where she could rent or buy a walker. She was falling behind in her physical therapy treatment and she thought the walker would help.

The Centers for Disease Control and Prevention estimates that three-quarters of the population will be overweight or obese by 2030. That puts us among the world's most obese countries, although Mexico surpassed the U.S. in 2013. In the U.S., black women and Hispanic men have the highest levels of obesity. And, what's more, almost 20 percent of children aged 6 to 11 were obese in 2008 — triple the 6.5 percent in 1980.

So what are the causes? First of all, we eat more meat than almost any other country. And we are drowning in fast food: Around one-third of children aged 4 to 19 eat some kind of fast food every day. Did you ever see the documentary Super Size Me? It was about a man who ate only at McDonald's every day for a month. He gained 11 kg and his cholesterol shot up.

Americans also drink more soda and sweetened drinks, our lifestyles are more sedentary, and there's been a jump in our "screen time" — the time we spend watching TV, sitting at a computer or playing video games.

So what can be done? Well, some schools have banned vending machines that sell high-calorie drinks and sugary snacks.

But for people who want to take personal control to keep their weight normal, here's my advice: Eat more fruits and vegetables; eat whole-grain bread or brown rice; exercise at least 30 minutes every day; cut down on fatty or sugary foods; and use vegetable-based oils when cooking.

If you need motivation, check out a photo that went viral on the internet recently. It showed the outside of a gym. There was a short staircase up to the entrance. On either side of the staircase was an escalator for gym members who were too lazy to climb a few steps.

Whatever you do to get fit, just remember: Don't get fat! (Oops — sorry, I shouldn't have used that word).